Rapid Communication: Dietary selenium improves skeletal muscle mitochondrial biogenesis in young equine athletes.

This study investigates the effects of selenium supplementation on the mitochondrial adaptation in the muscles of young horses undergoing physical training. The research found that elevated dietary selenium may enhance muscle mitochondrial growth and function, which could positively affect the health and performance of equine athletes.

Study Design

• The researchers enlisted 30 American Quarter Horse yearlings for this study. The horses were divided into two groups: one that underwent exercise training and another that did not.
• Within these two groups, the horses either received 0.1 or 0.3 mg Selenium (Se) per kg of their diet for 14 weeks.
• The study had two phases (weeks 0 to 8 and weeks 9 to 14), and half of the trained horses switched to the opposite dietary treatment in phase 2.
• At the end of each phase, all horses had to pass a 120-minute submaximal exercise test.
• Biopsies of their middle gluteal muscle (a muscle in the buttocks) were collected before and after each study phase and after each exercise test. These samples were analyzed for markers indicating the number and function of mitochondria (the cell’s powerhouses).

Study Findings

• The horses that received 0.3 mg Se per kg of diet had higher mitochondrial content at rest, indicated by increased activity of the enzyme citrate synthase.
• Activity of cytochrome oxidase (CCO), another enzyme important for mitochondrial function, was not generally affected by dietary Se. However, horses that were transitioned to a lower Se diet during Phase 2 showed a decrease in integrated CCO activity, suggesting possible impairment in mitochondrial function.
• Rapid, strenuous exercise bouts did not affect mitochondrial enzyme activities.
• The relatively low-intensity exercise protocol used in the study did not induce functional mitochondrial adaptations. However, dietary selenium seemed to facilitate mitochondrial growth during development and training.

Conclusions and Future Directions

• This research is an early step and further investigations are needed to understand the potential benefits of selenium supplementation for elite equine athletes. Portraying a more strenuous exercise training protocol in further studies could help to bring out these benefits more obviously.
• Still, the study indicates that selenium, an antioxidant, might be beneficial for young horses as part of their diet, improving their fitness and health by boosting the function and growth of mitochondria in their muscles.